(Kim Komando, Special for USA TODAY) — Have you ever had the feeling that someone was following you? Or maybe you were out with a group and suddenly find yourself surrounded by strangers. It’s not safe to go for a walk, shop, exercise, or drive alone anymore.

You have one gadget that can let others watch over you and in the event of an emergency, summon help. But your phone must have the tools before you need them.

After you read about the tools, take the next step and put them on your phone. It may save your life someday. Be sure to share this article with family and friends, especially anyone living alone and college students. Just remember, nothing is a substitute for common sense and good planning.

Reach out to friends or the local police for help

When you are walking alone, use the Companion app (Apple, Android; Free). The premise is simple, but the execution is genius.

You start by entering your destination. Next, add friends or family members as your companions. Anyone can be a companion. They don’t need to have the app installed on their phone.

Companions receive a text message with a link to an online map showing your destination. The map refreshes as you move and shows your position in relation to your destination. When you arrive safely, your companions receive a confirmation message.

Along the way, if you are uneasy, you can tap the “I feel nervous” button. Your companions get a notification to call you.

If you go off course, fall, start running or suddenly remove your headphones, the app asks if you're all right. You have 15 seconds to press a button saying you're fine.

If you don't push the “I’m Okay” button, the app sounds an alarm and gives you the option to contact the police.

Keep the police on standby

Have you ever been in a situation where you question whether it’s dangerous enough to call 911? Instead of worrying yourself with indecision, use SafeTrek.

The app works like a dead-man switch (which sounds awful, but that's what it is). Simply tap and hold the screen to put a call to the police on standby.

If something bad does happen, release the screen and the police are called. Unless you enter the disarming PIN in 10 seconds, the police automatically get the message that you're in trouble along with your location.

SafeTrek is free to download, but there is a $2.99 monthly service fee for both Android and Apple.

Send alerts if you don't check in

A check-in buddy is a time-tested, low-tech way to let a trusted friend or family member know that all is well. KiteString makes checking in as easy as sending a text message.

You need to initiate your first trip using the KiteString website. Afterward, you can initiate future trips by sending a text message such as "15m" to request a check in 15 minutes later.

If you don't respond with an "OK" after five minutes, KiteString will automatically send an emergency alert to your selected contact. Because it uses text messaging, it works with just about any phone, not just smartphones.

The free version of KiteString limits you to 15 trips per month and one emergency contact. The paid version costs $3 per month for unlimited trips and contacts.

Bonus: Samsung's built-in safety feature

If you own a Samsung Galaxy S5, S6, S7 or Note, it has a little-known emergency tool called Safety Assistance.

In an emergency, press the Power button on your phone quickly three times, and your phone will pause and vibrate. The recipients of your emergency alert will receive a text that includes your GPS location, photos taken from the front and rear cameras, as well as what the phone’s microphone picks up in a short recording.

In your phone's Settings menu, tap Quick Settings, Privacy and Emergency, and then Send SOS Messages. These steps may vary slightly depending on your smartphone and its operating system.